During certain interventional proceedings, e.g. those involving the insertion of an intravascular catheter, patients are required to lay supine on an X-ray procedure table. The physician then inserts an intravascular catheter through a small incision made in the patients arm or groin, which is then guided to the desired location.
To facilitate this process the tip of the catheter is X-ray opaque, allowing the physician to guide the catheter under fluoroscopic observation.
Fluoroscopic observation is a real-time imaging technique involving placing the patient between an X-ray emitting tube and an image intensifier or digital detector. Typically the X-ray tube is carried by the lower end of a C-shaped arm with the detector positioned at the other end. Such C-arms are freely moveable to permit a wide range of radiographic views of the patient.
During a procedure the physician passes the catheter through the patient and tracks its location on a monitor, which gives a visual representation of the radiation received by the digital detector. Typically the X-ray tube is located underneath the table and the physician moves the C-arm accordingly to continue tracking the location of the catheter as the procedure continues.
Although the majority of the X-rays pass through the table, to the patient and to the detector, inevitably there is some scatter. As such interventional procedures often take an extended time to complete, this has the potential to may expose the physician to a significant amount of radiation.
To reduce exposure to radiation, a number of X-ray protection table mounted shields have been developed, for example those shown in U.S. Pat. No. 5,006,718 and U.S. Pat. No. 5,981,964, which involve a flexible X-ray curtain positioned between the physician and patient and extending from the side of the table to the floor. Such shields have a horizontal hinge to allow the shield to be repositioned to allow for the passage of a C-arm during a procedure.
However, inevitably there will be occasions where, for whatever reason, the shield is not repositioned during movement of the C-arm, resulting in a collision between the C-arm and shield. For example, the position of the shield may not be apparent if it is covered with sterile drapes, as often happens. Additionally the physician will be concentrating on the procedure to hand and may not realise that movement of the C-arm may result in a collision.
Such C-arms are often fitted with collision detection devices for safety reasons, however even though this may reduce the risk of damage to equipment, the procedure will be interrupted and may result in its cancellation.